A belt-type continuously variable transmission including a drive pulley, a driven pulley, and a metallic belt wound around the two pulleys is conventionally known (for example, see Japanese Patent Application Laid-Open No. H6-307510).
FIG. 7 shows a deviation Δe in longitudinal center line of a metallic belt 97 in a cross section including the center axes of a drive pulley 98 and a driven pulley 95, in the case where the contact surfaces (hereafter referred to as “V surfaces”) between the respective drive pulley 98 and driven pulley 95 and the metallic belt 97 in the cross section are linearly shaped. As shown in FIG. 7, when the gear ratio is changed from maximum (LOW ratio) through intermediate (MID ratio) to minimum (overdrive (OD) ratio), the metallic belt 97 moves in the direction of the center axes of the drive pulley 98 and driven pulley 95 according to changes in width of the pulley grooves of the two pulleys 98 and 95. Here, since the amount of movement of the metallic belt 97 differs between the drive pulley 98 side and the driven pulley 95 side, the deviation Δe in longitudinal center line of the metallic belt 97 changes in the right-left direction, and the orientation 99 of the metallic belt 97 fluctuates right and left (this deviation in longitudinal center line of the metallic belt 97 is hereafter referred to as “misalignment”).
If the metallic belt is misaligned in this way, uneven wear occurs in the contact surfaces (V surfaces) between the respective drive and driven pulleys and the metallic belt, or the metallic belt is twisted and as a result decreases in durability.
In Patent Literature 1, misalignment is prevented in the following manner. The inclination angle (the angle with respect to a plane perpendicular to the center axis of the pulley) of the generatrix on the outer diameter side of the pulley is set larger than the inclination angle of the generatrix on the inner diameter side of the pulley to widen the pulley groove, while the boundary portion between the outer diameter side and inner diameter side of the pulley is shaped as a smooth convex curved surface. The side edge of the body portion of each element of the metallic belt is formed in correspondence with the pulley in such a manner that the angle on the outer diameter side of the metallic belt is set to make line contact with the inner diameter side of the pulley and the angle on the inner diameter side of the metallic belt is set to make line contact with the outer diameter side of the pulley.
A continuously variable transmission in which the generatrix from the inner diameter side to outer diameter side of the pulley is a smooth curve to prevent misalignment is also known (for example, see Japanese Patent Application Laid-Open No. 2002-31215).